Its common sense to look after your jet.
Sure you can take off at rated power all the time if you want you can also deploy the flaps at limiting speeds all the time. Same end result, they will fail more often perhaps with catastrophic results. So you have to figure whether any added safety margin due to reduced time on the ground outweighs the negative of an increased number of failures. The judgement of clever people who look into all this is that reduced thrust take offs are safer and cheaper than the rated alternate. You can disagree if you like SSG but I first suggest you write to the engine and aircraft manufacturers and ask the same question.
Remember too you can often have a spread of V1s depending on whether your operator is go or stop minded.
Also operators specify when you must use rated thrust eg contamination, strong winds, unserviceabilities etc to cater for situations when the risk benefit balance shifts the other way. Limits are also placed on the maximum reduction allowed. I think its 25% but I could be wrong on that number.
The calculations are normaly very conservative. We don't normaly take any benefit from a headwind or QNH (although we could) and allow for 1.5 times a tailwind and correct for a low QNH. If your taking these comfort factors out its because your payload critical and will be rated power in any case.
As others have said if you lose an engine you can increase power if you wish to give more margin but SSG you must understand this is not required to continue safely. You can stick with the reduced thrust if you so wish.
The Airforce do it too by the way.
SSG Reaction times are not reduced. You stop up to V1, at or after it you keep going. Same decision same reaction time wherever on the runway you happen to be. Less runway left certainly however I very much doubt if it makes anything like 5000' of difference as you have a limit to how much you can reduce by and in reality the derates are often not that large.
Horse it off the runway? You need to get this cowboy mentality out of your head SSG. I've had many engine failures in the sim at V1 and have never horsed the aircraft anywhere. Always a smooth rotation and the aircraft has done as it should so maybe the people who build the sims are in on the bill of goods as well.
The vast majority of airliners now have FADEC or EECs of some type that will look after the engines so overboosting is not an issue now for the vast majority.
Out of interest, as I have no experience of Business Jets, do they operate to Perf A? Some of them? All of them?